Method of processing lubricating



Patented July 17, 1951 METHOD OF PROCESSING LUBRICATING OIL BY TREATINGWITH SULFURIC ACID, A PHOSPHORUS SULFIDE AND CLAY, AND THE RESULTINGPRODUCT John D. Bartleson, East Cleveland, Ohio, assignor to TheStandard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing.Application May 29, 1948, Serial No. 30,204

Claims. i

This invention relates to processes of improving hydrocarbon baselubricants, and more particularly to the treatment of hydrocarbonlubricants with sulfuric acid followed by the treatment thereof with asmall amount of a phosphorus sulfide, to form lubricants having improvedproperties, especially as to corrosion, lacquer, sludge, viscosityincrease, and the like characteristics. It also relates to the resultingimproved lubricants.

Many of the commercially used lubricants are based upon hydrocarbonstocks, which may be synthetically prepared or which may be derived fromnatural sources, such as petroleum. For many purposes so-calledadditives must be included with the hydrocarbon in order to provide alubricant having suitable characteristics. This is especially so in thecase of acid refined stocks. Generally the inclusion of such additivesis associated with a higher cost of the finished lubricant. Thepreparation of a finished lubricant directly from hydrocarbon stock by achemical finishing or refining process (which does not involve solventextraction) at a commercially interesting cost has been a particularlybaiiling problem to the art.

In accordance with the invention, it has been found that hydrocarbon,lubricating oil stock may be refined by treatment with sulfuric acid inthe conventional manner, and then may be further refined with a smallamount of a phosphorus sulfide, and the resulting refined product is animproved lubricant; i. e., a chemically finished or refined lubricant. Aclay treatment is included before or after the sulfide refining. Suchlubricants are suitable for use under various conditions, including hightemperatures or high pressures or both; as, for instance, use in aninternal combustion engine operating at high temperatures and in whichthe lubricant is in close contact with metallic surfaces, metalcompounds and high temperature gases. They are also suitable for use inextreme pressure lubricants, e. g., in oils and greases containing thesame.

Treatment of the hydrocarbon oil with sulfuric acid may be carried on inthe conventional manner, e. g., using from 1 to 100 lbs. of the acid perbarrel of oil, at a treating temperature in the range of 32 F. to 300 F.A sludge or acid layer is removed. This step is long and well-known inthe art. The resulting hydrocarbon oil is treated with the phosphorussulfide. This may be conducted with direct admixture, or, if desired, bytheir admixture in the presence of a diluent which may be subsequentlyremoved. Generally a diluent is not necessary. The reaction or treatingtime is usually complete in about 10 hours or less time, generally 1 to2 hours. The

time is a function of the temperature, the amount of sulfide that is toreact, the subdivision of the reactants, the efiiciency of mixing thereactants, and the like.

The hydrocarbon lubricant stock is reacted with the phosphoruspentasulfide in a ratio of from about 0.1 to about 0.75% by weight,based on the weight of the hydrocarbon stock, and preferably about 0.25to 0.6%. If a higher amount of the sulfide is used,.such as 1%, some ofthe characteristics of the resulting product are worse than the initialhydrocarbon oil, especially the viscosity increase. At least about 0.1%of the sulfide should be used to achieve the results desired on acommercial scale, although small amounts show improvement.

The treatment of the hydrocarbon with the phosphorus sulfide may becarried out in the presence or absence of air, or in an atmosphere ofinert or non-deleterious gas, such as nitrogen or Has. It may also becarried out under pressure, e. g., pressure from the inert gas or thatgenerated when the reaction is carried out in a closed vessel.

The sulfide treating temperature varies withv the hydrocarbon stock.Generally the temperature should be at'least 275 F., but should be belowthe temperature at which the reaction product would be decomposed. Atemperature in the range of, about 300 to about 450 F., is preferred inmany cases. The finally treated oil is preferably centrifuged orfiltered to remove any by-products, sludge, or other by-productmaterial. If a volatile diluent is used, it may be removed byevaporation.

The stock is clay treated before or after the sulfide refining, i. e.,after the acid treatment, or after the P285 treatment, or both.Treatment after the PzSs refining is preferred if only one claytreatment is given. The amount of clay is not critical. Any amount givessome improvement and the effect levels off with large amounts. Generallythe amount will be 2 to 25 lbs. per barrel of oil (about 300 pounds) andpreferably 6 to 18.

The hydrocarbon lubricant stock to which the process is applied may be araw oil, i. e., a fluid hydrocarbon having a viscosity at F. of 10 to500 centistokes, such as that used as the base for the S. A. E. 10 to 50oils. It may be obtained as a distillate or from synthetic material,such as petroleum, and oils produced by cracking, polymerization,hydrogenation, and the like methods.

In order to illustrate and point out some of the advantages oftheinvention; but inno sense as a limitation thereof, the followingspecific embodiments are included.

In the following examples #300 Red Oil (a':

with the kind and amount of phosphorus sulfide indicated in thefollowing table,;agitated-ford hour at 300 F., at atmospheric pressure.A. good yield is obtained, based on the hydrocarbon lubricating oil, andno sludge is formed in the phosphorus sulfide treating step. However, itis a preferred to filter the-final reaction product. In some-of theexamples the clay treatment is usedbefore (third column), or after-(last column) or both, the phosphorus sulfide treatment, using theamounts of clay as indicated in the following table. The reactionproduct is identified hereinafter by the example number.

4 then with the clay makes some characteristics much worse than the rawoil alone, especially the viscosity increase, as shown on sample B anddoes not. materially help; Treating. the raw oil with the. phosphorussulfide, and .then'with the acid, makes some characteristics worse thanthe raw oil alone, especiall the pentane insolubles andthe viscosityincrease, as shown on sample C. This indicates thatthe phosphorussulfide treatment.-must follow the acid treatment, asillustrated-byiExample 1.

In the following examples an S. A. 20 oil was used and the'treatment isevaluated in the table.

Amount-of 93 per cent ea Kind and Amount gF 'g f' E Sulfuric y ofPhosphorus 8011- 3 sample 111 Lbs. s m Lbs umber Acid in er fidc 1n pe.cent by H Lbs. per g Weight of Hydro 1 Barrel 1 carbon Oil 0 o1 0.1 ofon o 15 I s 0.2% ms; at 300 F; 7 l 8 0.2% P153 at 400 F 8 8 0.4%

The Sohio Corrosion Test was used in evalu-" ating lubricants made inaccordance with the in; vention. This test is described in a copendingAmount of Kind ml application of E. C. Hughea'J. D. Bartleson, MJL. 93 i-F Amount olPhos- 9".' Sunday and M. M. Fink, which also correlates the.Example a Sh Phmls Sulfide St res lt of th laborat r tests withaChevrolet Number: Le. 2. asst by S 8 Y Barrel). Oil Weight of Hydro- Oilengine test.

on Essentially the laboratory test equipment con sists of a verticalthermostatically heated glass 10 0.4% rzsfl s test tube mm. outsidediameter and 42 cm: is --g"-" long), into which is placed the corrosiontest 10 5.1% 1 4's; 7.2 unit. An air inlet is provided for admitting airgg 5: 31 i into the lower end-of the corrosion unit in such 10 8 do...None a way that in rising the air'will cause the oil and 30 15 40suspended material therein to circulate into the 1 Theacid treatment inthis case is afterthe P285 treatment.

laboratory test procedures, as described in United States. Patent No.2,403,474 at column 7, line 19 et seq; using the Standard test at 280 1for 36 corrosion unit. The tube is filled with an amount of the oil'tobe tested which is at least sufiicient to submerge the metals beingtested.-

Thecorrosion testunit essentially'consists in a circular relatively finegrained copper-lezid test piece of O. D., which has a flfl'diameter holein its center (i. e., shaped like an ordinary'washhours. The resultsgiven in Table I are repreer).- The test piece has anexposed-copper-lead sentative. surface of 3.00 sq. cm. Of this surfacearea, 1.85

Table I Lubricant Example No A 1 2 3 4 5 B C Lacquer Deposit (inMgmsz).89.6 8 12. 2 2.0. 1 0 0 60.9 66.7 Corrosion (in' mgms.) Wt.

loss 0f-O'u-Pb 16.4 l.'2' 2. 5 4 5. 7 1. 2 9. 3 1-4. 8 Pentanelnsolubles (in mgnL/lfl g. of lubricant) 3 85 185 216 88.5 89.3 135.0643 794' Acid Number; 4.6 1.6 'l.8 1.6 0.41 0.41 6.9; 7.3 ViscosityIncrease (SUS) 362 81 73 64 10 76 888 398 Appearance Rating D A B- A 13+13+ D C sq. cm: acts as a loaded bearingyand'is contacted by a part ofthe cylindrical surface of a'hardened steel drill rod'-(14" diameter andlong, and of 51-57 Rockwell hardness);

The drill rod is held in a special holder; and the holder is rotated sothat the surface of the drill rod which-contacts the bearing sweeps thebearing surface (the drill rod is not rotated on its own axis and thesurface of the drillrod which contacts the bearing is not charged) Thecorrosion test unit means for holding the bearing and the drill rod is asteel tubing (15 long and I O. D.) which is attached to 'a support. Asteel cup (1" long,"1 %f O. Dfibyi Merelytreating the raw oil-with theacid and I. D.) is threaded into the steel'tubegat thelower end. The cuphas a diameterholein the bottom for admitting the oil into the corrosionchamber. Th copper-lead test piece fits snugly intothe steel cup and thehole in the test piece fits over the hole in the steel cup. A section ofsteel rod in diameter and 19" long) serves as a shaft and is positionedby 2 bearings whichare fixedly'set in the outer steel tubing, one nearthe top and one near the lower (threaded) end thereof. Several holes aredrilled just above and just below the lower hearing The holes above thebearing facilitate cleaning the apparatus, while the holes below thebearing enable the circulation of oil through the corrosion chamber. Thedrill rod holder is connected to the shaft by 'a' self-aligning yoke andpin coupling. This assures instantaneous and continuous alignment of thedrill rod bearing member against the bearing surface at all times. Apulley is fitted to the top of'th'e steel shaft and the shaft isconnected therethrough to a power source. The shaft is rotated at about6'75 R. P. M.; and the weight of the shaft and attached members is about600 grams, which is the gravitational force which represents the thruston the bearing. The air lift from the air inlet pumps the oil throughthe chamber containing the test piece and out through the holes in thesteel tubing.

The ratios of surface active metals to the volume of oil in an internalcombustion test engine are nearly quantitatively duplicated in the testequipment. The temperature used is ap proximately that of the bearingsurface. The rate of air flow per volume of oil is adjusted to the sameas the average for a test engine in operation. Of the catalytic effects,those due to soluble iron are the most important. They are empiricallyduplicated by the addition of a soluble iron salt. Those due tolead-bromide are duplicated by its addition.

The test was correlated with the L4 Chevrolet test and a slightlymodified version thereof. The modified test comprised reducing the oiladditions from the 4 quarts in the usual procedure to 2 quarts, byreducing the usual 1 pint oil additions which are made at 4 hourintervals to pint additions. This modification increases the severity ofthe test in its corrosion and detergency components, particularly in thecase of border line oils.

For each test, the glass parts are cleaned by the usual chromic acidmethod, rinsed and dried. The metal parts are washed with chloroform andcarbon disulfide and polished with No. 925 emery cloth or steel wool. Anew copper-lead test piece is used for every test. The test piece ispolished before use, on a surface grinder to give it a smooth finish.The test piece is weighed before and after the test on an analyticalbalance to evaluate the corrosion. After placing the oil and corrosiontest unit in the tube, and bringing the assembly up to temperature inthe thermostat, soluble catalyst is added and the air flow is started.Lead-bromide catalyst is added immediately after starting the air, andtiming of the test is begun.

The laboratory test conditions which were found to correlate with theChevrolet procedure 36-hour test are shown in the following table.

Table A Temperature-325 F.

Oil sample107 cc.

Air flow rate- 70 liters/hour 'Iime10 hours 6 Catalysts-Stee1;Copper-lead bearing. 3 sq. cm. area of which 1.85 sq. cm. is a bearingsurface; ferric 2-ethyl hexoate: 0.05% as FezOa in C. P. benzene; leadbromide: 0.1% as precipitated powder. Bearing assembly Load -grams 600Speed --R. P. M. 675

By extending the laboratory test to 20 hours, it was found thatcorrelation with the Chevrolet 72-hour test could be obtained.

At the close of the test period, the extent of corrosion is determinedby reweighing the corrosion test piece and determining the change inweight due to the test. An accurate evaluation of the. lacqueringproperties of an oil is obtained by a visual rating system which isapplied to the outer surface of the corrosion unit steel tube and metalcup in much the same way that the piston skirt, cylinder wall, etc., ofan engine are rated for varnishes. The sludge rating of the engine issimulated by a visual rating of the insoluble materials and used oilwhich are coated on the glass test tube at the conclusion of the test.For both sludge and varnish rating a scale rating of A (best) to F(worst) is used.

A sufiicient volume of used oil is obtained from the test for.determination of the usual used oil properties, such as pentaneinsolubles (sludge), viscosity increase, neutralization number andoptical density.

V The data in the following tables typify the results obtained in20-hour Sohio corrosion tests on the hydrocarbon lubricating oil basestock, and the improved lubricants prepared therefrom in accordance withthe invention.

These Table II data also show the marked improvements achieved inaccordance with the invention using the sesquisulfide. It may be notedthat the 400 F., reaction temperature used in Example 7 does notappreciably improve the reaction product, as compared to the 300 F.,reaction temperature of Example 6.

By comparable procedures, using any known comparable phosphorus sulfide,or amount of phosphor-us sulfide, or hydrocarbon lubricating oil stock,within the broad types and ranges as indicated hereinbefore, comparableimproved lubricants are obtained.

If desired, the improved lubricants of the invention may be used inblends together with other lubricants or lubricant agents, e. g., withsoap or the like in a grease. If desired, an agent for improving theclarity of the oil may be included, e. g., lecithin, lauryl alcohol, andthe like. If desired, an agent for preventing foaming may be included,e. g., tetraamyl silicate, an alkyl ortho-carbonate, ortho-formate orortho-acetate, or a polyalkyl silicone oil.

In view of the foregoing disclosure, variations and modifications of theinvention will be apparent to those skilled in the art, and it isintend- 7 ed to claimsuch variations and"'-modifi'cati6fis broadly,except'as'do not 'come -within -th scope ofthe appended claims."

I claim:

1. A method of processing lubricating' oil stock consisting essentiallyof hydrocarbo i mate'rial to yield an -oilhaving improved-inhibition tooxidation in service, which method comprises treating said stock withsulfuric acid inaconventional manner, then treating the resultingacid-refined hydrocarbon with an amount in'the range of about 0.1 toabout"0.75% by Weight of a phosphorus-sulfide at a temperature in therange of about-275 -to 450 F., and including. a separate clay-treatingstep subsequent to the acid-refining step.

2. The method of claim.1 wherein the hydrocarbon is treated with anamount of phosphorus pentasulfide in the range of about 0.1 to about0.75%.

3. The method of claim 1 wherein the hydrocarbon is treated with anamount of phosphorus sesquisulfide in the range of about l1'to about0.75%.

4. The method of claim3 wherein' the'hydi'ocarbon is treated with anamountof phosphorus sesquisulfide in the range of about 0.1 to about0.6% at a temperature of about'300? td 450 F.

5. The method of claim 2 wherein 'the" claytreating step is subsequentto the phosphorus pentasulfide treating step.

6. The method of claim- 2 wherein-the'claytreating step is just prior tothe phosphorus pentasulfide treating step. i

7. The method of claim 5 wherein the hydrocarbon is treated With anamount'of phosphorus pentasulfide in the range of about 0.25'to about0.6% at a temperature in the range of about 300 to 450 F.

8. The method of claim 6 followed by an additional final treatment withclay.

:9. Thef'methodtofclaim 8- whereinzthvhydrocarbon is treated with anamount of phosphorus pentasulfide in. the range of about 0.25 to-about0.6% at a temperature in the range of about 300 to'450" F.

10; The method of claim 9 wherein-the amount of the phosphoruspentasulfide is 0.4%.

11; The'refine'd lubricating oil obtained by the process of claim 1.

12. Therefined lubricating oil obtained' by'the process of claim 2.

13. The refined lubricating oil obtained the. process 'of claim 3.

' 14. The refined lubricating oil' obtained-by the process .of. claim 4.g

15. The refined lubricating oil obtained by: the processzof claim 5.

\ 16; The refined lubricating oil obtained-by the process of claim 6.

17; The re'fined'lubricating oil obtained [bye-the process of claim 7.

118. The refined lubricating oil obtained-bythe process of claim 8.

19.:The r'efined lubricating oil obtained bythe process'of claim 9.

20. The refined lubricating"oilobtainedby the process of claim 10.

JOHN D. BARTLESON.

REFERENCES CITED 'The following references are of record in -the me ofthis patent:

' UNITED STATES PATENTS

1. A METHOD OF PROCESSING LUBRICATING OIL STOCK CONSISTING ESSENTIALLYOF HYDROCARBON MATERIAL TO YIELD AN OIL HAVING IMPROVED INHIBITION TOOXIDATION IS SERVICE, WHICH METHOD COMPRISES TREATING SAID STOCK WITHSULFURIC ACID IN A CONVENTIONAL MANNER, THEN TREATING THE RESULTINGACID-REFINED HYDROCARBON WITH AN AMOUNT IN THE RANGE OF ABOUT 0.1 TOABOUT 0.75% BY WEIGHT OF A PHOSPHORUS SULFIDE AT A TEMPERATURE IN THERANGE OF ABOUT 275* TO 450* F., AND INCLUDING A SEPARATE CLAY-TREATINGSTEP SUBSEQUENT TO THE ACID-REFINING STEP.